It affords some indication of the local estimation in which Watt was held, that the magistrates of Glasgow should have selected him as a proper person to survey a canal for the purpose of opening up a new coal-field in the neighbourhood, and connecting it with the city, with a view to a cheaper and more abundant supply of fuel. He also surveyed a ditch-canal for the purpose of connecting the rivers Forth and Clyde, by what was called the Loch Lomond passage; though the scheme of Brindley and Smeaton was eventually preferred as the more direct line. Watt came up to London in 1767, in connexion with the application to Parliament for powers to construct his canal; and he seems to have been very much disgusted with the proceedings before “the confounded committee of Parliament,” as he called it; adding, “I think I shall not long to have anything to do with the House of Commons again. I never saw so many wrong-headed people on all sides gathered together.” The fact, however, that they had decided against him had probably some share in leading him to form this opinion as to the wrong-headedness of the Parliamentary Committee.
Though interrupted by indispensable business of this sort, Watt proceeded with the improvement of his steam-engine whenever leisure permitted. Roebuck’s confidence in its eventual success was such that in 1767 he undertook to pay debts to the amount of 1000_l._ which Watt had incurred in prosecuting his project up to that time, and also to provide the means of prosecuting further experiments, as well as to secure a patent for the engine. In return for this outlay Roebuck was to have two-thirds of the property in the invention. Early in 1768 Watt made trial of a new and larger model, with a cylinder of seven or eight inches diameter. But the result was not very satisfactory. “By an unforeseen misfortune,” he wrote Roebuck, “the mercury found its way into the cylinder, and played the devil with the solder. This throws us back at least three days, and is very vexatious, especially as it happened in spite of the precautions I had taken to prevent it.” Roebuck, becoming impatient, urged Watt to meet him to talk the matter over; and suggested that as Watt could not come as far as Carron, they should meet at Kilsyth, about fifteen miles from Glasgow. Watt replied, saying he was too unwell to be able to ride so far, and that his health was such that the journey would disable him from doing anything for three or four days after. But he went on with his experiments, patching up his engine, and endeavouring to get it into working condition. After about a month’s labour, he at last succeeded to his heart’s content; and he at once communicated the news to his partner, intimating his intention of at last paying his long-promised visit to Roebuck at Kinneil. “I sincerely wish you joy of this successful result,” he said, “and hope it will make some return for the obligations I owe you.”